1. Field of the Invention
The present invention relates to an image capturing apparatus, an image capturing method, and a computer program, particularly used for performing an exposure operation.
2. Description of the Related Art
Hitherto, various strobe camera systems for performing an exposure operation by adjusting the amount of light emitted to a subject in order to automatically obtain adequate exposure have been proposed. Among those systems, the following type of system is effectively used for responding to various situations of a picture frame. That is, in the system, preliminary light emission is performed prior to exposure, light reflected from a subject at the preliminary light emission is measured for each area in a picture frame, and the amount of light to be emitted at actual light emission is controlled based on the measurement result.
U.S. Pat. No. 5,309,193 discloses the following method. The light reflected from a subject at preliminary light emission is measured in each of a plurality of areas in a picture frame. Among those areas, areas where the measurement value is outside a predetermined range are eliminated from the target of calculation of the amount of light for actual light emission. Also, the amount of light to be emitted at the actual light emission is determined by adding a predetermined correcting value to the value of reflected light at the preliminary light emission.
On the other hand, U.S. Pat. No. 6,349,175 discloses the following method. That is, a weighting coefficient of each of a plurality of areas in a picture frame is determined based on the level of the reflected light at preliminary light emission, and weighting for the amount of light to be emitted at actual light emission is averaged by using the determined weighting coefficients, and the amount of light to be emitted is determined accordingly.
In these known techniques, however, when a reflective object, such as a window, faces a picture frame, the light emitted from a strobe device and reflected by a subject makes the photometric value high. Therefore, when the amount of light to be emitted from the strobe device is controlled, the amount of light may be smaller than necessary so as to cause underexposure.
In another case, if a main subject in a picture frame is too small, the light emitted from a strobe device and reflected by the subject makes the photometric value low. Therefore, when the amount of light to be emitted from the strobe device is controlled, the amount of light may be larger than necessary so as to cause overexposure.